Chamber pump and method for operating a chamber pump

ABSTRACT

A chamber pump ( 10 ) and a method for operating same are provided. The chamber pump ( 10 ) includes a pump chamber ( 12 ), a chamber diaphragm ( 14 ) or a piston ( 34 ) as well as an axially movable driving rod ( 24 ) acting on the chamber diaphragm ( 14 ) or on the piston ( 34 ) for changing the volume of the pump chamber ( 12 ). The chamber pump ( 10 ) includes an electroactive diaphragm ( 40, 40′ ), which acts as an actuator for influencing an axial position of the driving rod ( 24 ) and acts on the driving rod ( 24 ), on the one hand, and on a housing of the pump ( 10 ), on the other hand. An electric potential is applied to the electroactive diaphragm ( 40, 40′ ) during the operation of the chamber pump ( 10 ) to influence an axial position of the driving rod ( 24 ) and to achieve a return stroke or a forward stroke of the chamber pump ( 10 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2016 014 832.2, filed Dec. 14, 2016, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a gas or liquid chamber pump hereinafter called pump for short. A reciprocating or diaphragm pump, in which a volume of a pump chamber, which volume is defined at least partly by means of the piston or the diaphragm and changes periodically during the operation based on a motion of a piston or of a diaphragm in the known manner and delivery of a respective medium and/or a pressure change upstream or downstream of the pump results from the periodical change in the volume of the pump chamber, is called a chamber pump. The present invention pertains to such a chamber pump intended for use in a medical device or in a safety system.

BACKGROUND OF THE INVENTION

Such a pump is used in a medical device, for example, to drive breathing gas, in order to transport measured gas, especially a patient gas, from a sampling point to a measuring point or to control or drive additional actuators. In relation to a use of such a pump in connection with an analysis of a patient gas, reference may be made to the suctioning patient gas monitoring in anesthesia and a so-called remote system in mobile personal gas-measuring technology. Such a pump is used in a safety system, for example, for a mobile or stationary analysis of harmful gases in the air. For example, measured gas is transported by means of the pump from a sampling point to a measuring point in this case as well. Moreover, such pumps are also considered for use in a medical device or in a safety system to generate auxiliary pressures. The invention being proposed here may also be used, in principle, for applications beyond medical devices and safety systems, for example, for measuring devices and analyzers. This is also always implied below without special reference.

Pumps of the type mentioned in the introduction are available in various embodiments, for example, with a crank drive or with a linear drive. Furthermore, pumps are known in which the drive is embodied as a piezoelectric drive. The particular drive acts on a diaphragm or on a piston in a particular pump head. The volume located in the pump head in the pump chamber (compression chamber) is changed periodically by means of the drive in both embodiments (diaphragm or piston). This leads to a volume transport as well as to pressure generation. The ratio of volume transport to pressure is determined by the geometry of the pump chamber, the stroke volume, the operating frequency, the switching characteristics of the valves needed and the external pneumatic load.

The working points of pumps currently available commercially for gases and liquids in an output range of 0 mbar to 110 mbar and at 200 mL/minute to 1,100 mL/minute or 0 mbar to 300 mbar at 200 mL/minute can be adapted by changing the stroke frequency in the case of a drive operated by means of an electric motor by changing the speed of rotation of the electric motor. A further adaptation must take place by an external pneumatic circuitry in the particular application. Different pump heads must be mounted in special cases.

A change in the stroke frequency affects the pulsation frequency and the percentage of change in the pressure curve. This is linked with the following disadvantages: On the one hand, conventional actions to suppress the pulsation, for example, a low-pass filter, lose their effectiveness. On the other hand, the avoidance of certain sensor-critical frequencies cannot be ensured. Finally, it is, on the whole, more difficult to coordinate a pneumatic system with the pump.

Especially high stroke frequencies (>100 Hz) mean extreme loads for the components of the pump. The losses due to valves, which no longer have low inertia, increase enormously. The phase of the closing angle of the valves becomes shorter or longer and is shifted in relation to the lifting motion of the piston or of the diaphragm. The percentage of flexing work in the seal (piston) or in the diaphragm increases drastically. Finally, a markedly increased noise generation of the pump in question is also associated with a high stroke frequency.

A continuous pressure curve is no longer guaranteed in case of low stroke frequencies (<10 Hz). Each pump stroke can be recognized as an increasing pressure pulse and also as a flow pulse. Attenuation or buffering by a buffer volume requires a very large buffer volume. A large volume distorts the gas fronts in case of changing gas mixtures. In case of a drive by means of an electric motor, this is in a critical working range at low stroke frequencies. Intermittent angular velocities with heavy wear on the brushes in the collector (in case of motors with brushes) are only one negative aspect. In addition, the speed is often too low for the build-up of a lubricating film in the bearings. Furthermore, the coils that are in use at the dead center of the pump shortly before the peak load are loaded more strongly, so that temperature peaks will develop in these coils. Finally, the moment of inertia of the rotor is insufficient to guarantee buffering of the load torque.

Even though linear pumps, which can be used as an alternative to pumps driven by electric motors, can be well regulated, they are markedly more inefficient due to their greater air gaps and require a higher output. Moreover, the operation of these pumps is associated with the development of a higher temperature. Such linear pumps are also markedly more expensive and require a greater manufacturing and maintenance effort, since an additional and above all fast sensor system is needed for detecting the position and/or the velocity of the drive for regulating the linear motion. Moreover, the compensation of the linearly moved masses necessary for a low-vibration run requires complicated constructions.

Piezoelectrically driven pumps are only suitable for miniature applications from the viewpoint of energy.

SUMMARY OF THE INVENTION

Based on the statements outlined above regarding the state of the art, an object of the present invention is to provide a linearly driven chamber pump that can readily be set and a method for operating same, which pump and method avoid at least some of the above-mentioned drawbacks or reduce the impacts thereof

This object is accomplished by means of a chamber pump (pump) according to the invention and in respect to a method for operating such a pump by a method according to the invention. At least one electroactive diaphragm, which is intended to influence an axial position of the driving rod and acts on the driving rod, on the one hand, and on a housing of the pump, on the other hand, is provided in a chamber pump of the type mentioned in the introduction, which comprises a pump chamber, a chamber diaphragm or a piston as means for cyclically changing the volume of the pump chamber during the pumping operation as well as a driving rod, which acts on the chamber diaphragm or on the piston for cyclically changing the volume of the pump chamber and is axially movable. The electroactive diaphragm or each electroactive diaphragm acts as an actuator in relation to the axial motion of the driving rod and at least partly replaces a prior-art drive of the chamber pump.

In a corresponding method for operating such a chamber pump or a chamber pump having individual additional features described below or a plurality of additional features described below, an electric potential is applied to an electroactive diaphragm, which acts on the driving rod, on the one hand, as well as on a housing of the pump or the like, on the other hand, to influence an axial position of the driving rod and to achieve a return stroke or a forward stroke of the chamber pump, namely, a return stroke or a forward stroke of the chamber diaphragm or of the piston.

A chamber pump is a cyclically operating machine for delivering liquids or gases. These will hereinafter globally be called medium. A pump cycle is known to comprise a return stroke and a forward stroke (or a forward stroke and a return stroke), and this continues in subsequent pump cycles. The at least one electroactive diaphragm mentioned is intended to achieve or to support a return stroke or a forward stroke. A special embodiment of the chamber pump being provided according to the invention is explained below, in which at least one electroactive diaphragm each is used to achieve or to support a return stroke (return stroke diaphragm) as well as a forward stroke (forward stroke diaphragm). As long as it is irrelevant whether the at least one diaphragm is intended to achieve or to support a return stroke or a forward stroke, reference is made to a partial stroke, wherein a complete pump cycle comprises a first partial stroke and a second partial stroke, for example, the return stroke and the forward stroke. The method for operating a chamber pump of the type outlined above is correspondingly characterized in that an electric potential is applied to at least one electroactive diaphragm, which acts on the driving rod, on the one hand, as well as on a housing of the pump or the like, on the other hand, to influence an axial position of the driving rod or to achieve a partial stroke of the chamber pump, namely, a partial stroke of the chamber diaphragm or of the piston.

The application of an electric potential to the at least one diaphragm brings about, in principle, in a manner known per se, a change in the so-called aspect ratio (ratio of thickness to area) of the electroactive diaphragm. In summary, an effective length of the at least one diaphragm changes due to the application of an electric potential between the fixed points thereof at the driving rod, on the one hand, and at a housing of the pump or the like, on the other hand. When the electric potential disappears, the original aspect ratio is restored and the effective length of the at least one diaphragm correspondingly decreases. The electroactive diaphragm is preferably prestressed. This leads to defined ratios. Without an electric potential being applied, an effective length corresponding to the prestress is obtained. When an electric potential is present, the effective length of the electroactive diaphragm is determined by the particular potential (the effective length increases with the electric potential present).

A periodic change in the effective length of the at least one electroactive diaphragm, which results from an alternating application of an electric potential to the at least one electroactive diaphragm, can be used to drive a chamber pump, namely, to drive a chamber diaphragm comprised by the chamber diaphragm or a piston comprised by the piston, without friction and noise as well as without wear. Moreover, very high stroke frequencies are advantageously possible as well.

Another advantage of the present invention is that such an electroactive diaphragm can be manufactured very cost-effectively and can be processed and applied automatically. Furthermore, such an electroactive diaphragm has a very small mass compared to conventional drives. This applies to both the percentage of the moving masses and the mass as a whole. The moving mass is an important reason why conventional linear drives cannot be used for many applications, above all for applications with high stroke frequencies. Contrary to the rotating masses of a motor, which can often be balanced in a simple manner, the mass of the armature moves in a so-called oscillating armature drive in the linear direction and thus it periodically displaces the center of gravity. This leads to vibrations and the generation of noise, which do not occur in case of a drive of the type being proposed here.

To simplify the language and in the interest of better comprehensibility, the following description will be continued on the basis of an optional embodiment, in which the at least one electroactive diaphragm, which acts on a driving rod, on the one hand, and, for example, on the housing of the pump, on the other hand, is replaced with precisely one electroactive diaphragm having these fixed points. Such an individual electroactive diaphragm in the form of a conical film/diaphragm acts, for example, in its center on the driving rod and is fixed on its sides, for example, on the pump housing, especially by clamping or bonding. Regarding the action on the driving rod, such an individual electroactive diaphragm has, for example, in its center, a hole, through which the driving rod or an area of the driving rod with a smaller diameter is led, the edges of the hole being fixed at the driving rod, for example, by clamping, bonding or the like. As an alternative to such an embodiment, an embodiment may be considered in which a plurality of diaphragms are used instead of an individual electroactive diaphragm, and these diaphragms are fixed each at the driving rod and extend radially outward from the driving rod and are fixed at the opposite end, for example, at the pump housing. The direction in which the force acts is determined by the location of the action on the driving rod as well as by the location of the action on, for example, the pump housing. Precisely one diaphragm and a plurality of individual diaphragms therefore have the same effect, if a location of action on the driving rod and a location of action on, for example, the pump housing are the same. This is presumed here. Whenever the precisely one electroactive diaphragm is mentioned, the alternative embodiment with a plurality of diaphragms acting in the same direction as the individual electroactive diaphragm is always implied as well.

In one embodiment of the chamber pump, this comprises a resetting element (or resetting arrangement). By means of the electroactive diaphragm acting as an actuator, a force can be applied to deflect the driving rod in a first direction and is applied during the operation of the chamber pump. A force can be applied by means of the resetting element to deflect the driving rod in a second direction opposite the first direction and is applied during the operation of the chamber pump. One of the two partial strokes (return stroke or forward stroke) of a complete pump cycle can be triggered by means of the electroactive diaphragm and is triggered during the operation of the chamber pump by means of the electroactive diaphragm (motion of the driving rod in the first direction). The complementary partial stroke (forward stroke or return stroke) can be triggered by means of the resetting element and is triggered during the operation of the chamber pump by means of the resetting element (motion of the driving rod in the second direction opposite the first direction). For example, a spring (compression spring or tension spring), in which the direction of the force is oriented opposite a force direction resulting from the electroactive diaphragm, may be used as a resetting element. A cyclical application of an electric potential to the electroactive diaphragm leads to a first partial stroke and the complementary second partial stroke is exerted by means of the resetting element. The resulting alternating triggering of first and second partial strokes leads to a pumping action. The pump comprises for this, for example, a control unit with at least one input, via which the partial stroke can be triggered based on the electroactive diaphragm, for example, sending the electric potential, which is to be applied to the electroactive diaphragm, to the control unit and hence to the pump at the respective input.

In a special embodiment of the chamber pump, precisely one or at least one additional (second) electroactive diaphragm acts as a resetting element in a special embodiment of the chamber pump. The above-mentioned simplification applies here as well, so that a second electroactive diaphragm will be referred to below in the interest of better comprehensibility, but without abandoning general validity, in this case as well. This second electroactive diaphragm likewise acts on the driving rod, on the one hand, and, for example, on a housing of the pump, on the other hand, especially in a form in which this was explained above for the electroactive diaphragm mentioned first. In a chamber pump with a (precisely one or at least one) first electroactive diaphragm acting as an actuator and with a (precisely one or at least one) second electroactive diaphragm acting as an actuator, these act each on the driving rod, on the one hand, and on the housing of the chamber pump or the like, on the other hand, and are intended to apply a force to the driving rod in an axial direction of the driving rod. The force that can be applied by means of the second electroactive diaphragm to the driving rod and is applied during the operation is directed antiparallel to the force that can be applied to the driving rod by means of the first electroactive diaphragm and is applied during the operation. One of the two partial strokes (return stroke or forward stroke) of a complete pump cycle can be triggered by means of the first electroactive diaphragm and is triggered during the operation of the chamber pump by means of the electroactive diaphragm (motion of the driving rod in the first direction) in such a chamber pump and in a method for operating such a chamber pump. The complementary partial stroke (forward stroke or return stroke) can be triggered by means of the second electroactive diaphragm and is triggered by means of the second electroactive diaphragm during the operation of the chamber pump (motion of the driving rod in the second direction opposite the first direction). The second electroactive diaphragm acts as a resetting element for the partial stroke triggered by means of the first electroactive diaphragm. However, the first electroactive diaphragm also acts in precisely the same manner as a resetting element for the partial stroke triggered by means of the second electroactive diaphragm. An alternating or at least phase-shifted application of an electric potential to the first electroactive diaphragm as well as to the second electroactive diaphragm leads to an alternating triggering of first and second partial strokes and hence to a pumping effect. The pump comprises for this, for example, a control unit with inputs, via which the first partial stroke and the second partial stroke can be triggered, for example, by sending the electric potential, which is to be applied to the first electroactive diaphragm and to the second electroactive diaphragm, to the control unit and hence to the pump at the respective input.

It is also possible to consider, as an alternative, an embodiment of a control unit, in which the control unit of the pump comprises, for example, a terminal for an electric potential and at least one input, wherein a set point for a desired pump position is set for the pump by means of the input, for example, in the form of a set point, which codes an indicator of a desired axial position of the driving rod. Based on the set point, the control unit of the pump then automatically determines an electric potential, which is to be applied to the electroactive diaphragm (or which is applied to the first or the second electroactive diaphragm or which is to be applied to the first electroactive diaphragm and to the second electroactive diaphragm) in order to obtain a pump position corresponding or at least essentially corresponding to the set point. The particular electric potential determined is generated automatically from the externally applied electric potential by means of the pump control. This is brought about, for example, by means of an electronic switch that can be actuated by means of a pulse width-modulated signal, for example, of a transistor, which is connected into a circuit with the electroactive diaphragm (or with the electroactive diaphragms) such that when the switch is closed, the potential applied externally is present at the electroactive diaphragm. Based on the pulse width-modulated signal used to actuate the switch, a potential that leads to the desired deflection of the driving rod is obtained over the electroactive diaphragm (or over the respective electroactive diaphragm). The basic frequency of the pulse width-modulated signal is selected to be high enough, for example, not below 1 kHz, so that it is ensured that individual pulses of the pulse width-modulated signal do not bring about any change in the aspect of the electroactive diaphragm.

In a special embodiment of the method, an electric potential is applied to the first electroactive diaphragm corresponding to a predefined or predefinable voltage profile and an electric potential corresponding to a predefined or predefinable voltage profile is applied to the second electroactive diaphragm by means of such a control unit or the like. By predefining the first and/or second voltage profile, for example, the duration of the first partial stroke and/or of the second partial stroke and hence, on the whole, the stroke frequency, the amplitude of the first partial stroke and/or of the second partial stroke and hence, on the whole, the stroke volume and/or the change over time in the volume of the pump chamber can be predefined. The essential parameters of a pumping operation can be set individually or in combination in this manner.

In a special embodiment of the chamber pump, the first electroactive diaphragm acts on the driving rod in front of the second electroactive diaphragm, namely, starting from the end of the driving rod acting on the chamber diaphragm or on the piston in front of the second electroactive diaphragm. A direction is defined by viewing the working points of the two electroactive diaphragms starting from the said end of the driving rod. The first electroactive diaphragm acts in this special embodiment along this direction on the pump housing or the like in front of its working point on the driving rod and the second electroactive diaphragm acts in the same direction behind its working point on the driving rod on the pump housing or the like. This makes possible a compact configuration of the chamber pump.

In another and especially preferred embodiment of a chamber pump of the type described here and below, the electroactive diaphragm—or in an embodiment with a first electroactive diaphragm and with a second electroactive diaphragm one of the two diaphragms or both diaphragms—acts as a sensor for obtaining position information concerning a position of the chamber diaphragm or of the piston. Just as an electroactive diaphragm changes its aspect ratio and especially its thickness when an electric potential is applied, the electric capacitance that can be measured between two electrodes placed on the surface of the electroactive diaphragm also changes with the change in the thickness. Such a signal is proportional to a particular effective length of the diaphragm The effective length of the diaphragm is, in turn, proportional to the axial position of the driving rod movable by means of the diaphragm, so that the measured capacitance is an indicator of the position of the driving rod and hence an indicator of the position of the chamber diaphragm or of the piston. Accordingly, a signal that can be obtained by means of a capacitance measurement is position information regarding the position of the chamber diaphragm or of the piston, which position is generally called pump position. Such position information may be used, on the one hand, as an actual value for a position of the pump and be made available, for example, to a higher-level system. Thus, this system always has information that is always current regarding the pump position and this can, for example, be displayed. The position information may, however, also be compared to an expected pump position and the result of the comparison can be outputted as state information or an error message may optionally be generated. The pump position may, in addition or as an alternative, also be used for controlling or regulating the pump. The control or regulation is implemented now, for example, in a control unit of the pump or in a control unit of a higher-level system. In case of such a control unit, the control unit continuously compares a respective set point for the position of the pump with the position information (actual value) representing the current position of the pump and generates, as a function of a possible deviation between the set point and the actual value, in a manner that is known per se, in principle, a manipulated variable for eliminating the deviation or at least for minimizing the deviation, namely, a manipulated variable by means of which the electric potential present on the electroactive diaphragm or on an electroactive diaphragm or on both electroactive diaphragms) is adapted.

In a special embodiment of a chamber pump, which comprises, on the one hand, both a first electroactive diaphragm for a first partial stroke and a second electroactive diaphragm for a second partial stroke, and in which measured value coding position information can be obtained, on the other hand, by means of a measurement on an electroactive diaphragm, provisions are made for the first electroactive diaphragm and the second electroactive diaphragm to act alternatingly as actuator and as sensor. An electric potential is then applied to the first electroactive diaphragm and to the second electroactive diaphragm in a cyclically alternating manner in order to obtain the first partial stroke and the second partial stroke. When, for example, an electric potential is applied to the first electroactive diaphragm and this leads to a change (increase) in the effective length thereof, this also influences, especially in case of prestressed diaphragms, the aspect ratio of the second electroactive diaphragm This change is, as was described above, measurable and, for example, a capacitance measurement yields position information. This is correspondingly also true when an electric potential is applied to the second electroactive diaphragm and the position information is determined by means of a measurement, especially a capacitance measurement, concerning the first electroactive diaphragm. The alternating use of one of the two diaphragms either as a sensor or as an actuator prevents distortion of the measurement for determining the position information based on an electric potential applied and accordingly guarantees especially reliable measured values regarding the position information.

The method as well as embodiments of the method and the method steps comprised by it are carried out automatically, i.e., without an action on the part of the user, i.e., for example, of a user of a medical device comprising the pump or the like. The automatic execution of the method steps takes place under the control of a control unit. This comprises, for example, a processing unit in the form of or in the manner of a microprocessor as well as a memory. A control program, which can be run by the processing unit, is or can be loaded into the memory, and this program is run during the operation by the unit of the memory. Thus, the present invention is also a pump with a control unit, where the control unit comprises an implementation of the method here and hereinafter described (for example, in software), it operates according to the method and comprises for this at least one control unit with an implementation of the method as a means for executing the method. The method is preferably implemented in software. Thus, the present invention is, on the one hand, also a computer program with program code instructions executable by a computer (the control unit or the processing unit thereof) and, on the other hand, a storage medium with such a computer program, i.e., a computer program product with program code means, as well as finally also a control unit, into the memory of which such a computer program is or can be loaded as a means for executing out the method and embodiments thereof.

Exemplary embodiments of the present invention will be explained in more detail below on the basis of the drawings. Objects or components corresponding to one another are designated by the same reference numbers in all figures.

The exemplary embodiment or each exemplary embodiment shall not be construed as a limitation of the present invention. Variations and modifications are rather possible within the framework of the present disclosure, especially such variants and combinations that the person skilled in the art can find in respect to accomplishing the object, for example, combining or modifying individual features described in connection with the general or special part of the specification and contained in the claims and/or in the drawings and that lead to a new subject through features that can be combined.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic sectional view showing a chamber pump with a crank drivel;

FIG. 2 is a schematic sectional view showing a chamber pump with an oscillating armature drive or with a spring as a resetting element;

FIG. 3 is a schematic view showing electroactive films and the result of an electric potential applied thereto;

FIG. 4 is a schematic sectional view showing a chamber pump according to an embodiment of the invention at an end of a return stroke (left) and at the end of a forward stroke (right);

FIG. 5 is a schematic sectional view showing a special embodiment of a chamber pump according to the invention;

FIG. 6 is a graph showing voltage profiles to be applied to an electroactive diaphragm for triggering a return stroke and a forward stroke;

FIG. 7 is a graph showing voltage profiles to be applied to an electroactive diaphragm for triggering a return stroke and a forward stroke;

FIG. 8 is a schematic sectional view showing different volumes of the pump chamber (partially defined by a chamber diaphragm) of the chamber pump as a result of different electric potentials;

FIG. 9 is a schematic sectional view showing different volumes of the pump chamber (partially defined by a piston) of the chamber pump as a result of different electric potentials; and

FIG. 10 is a schematic sectional view showing another special embodiment of a pump chamber being proposed here, in which electroactive films act either as actuator for triggering a return stroke or a forward stroke or as sensor for determining the position information of the pump.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, the views in FIG. 1 and FIG. 2 show in a schematically simplified manner two embodiments of a chamber pump 1, which will hereinafter sometimes also be called pump 1 for short, which embodiments are basically known per se. Each pump 1 has a pump chamber 12, which is defined by an elastic diaphragm 14, on the one hand, and by a housing part 16 of a pump housing, on the other hand, with at least one respective inflow opening and outflow opening formed therein. The diaphragm 14 hereinafter called chamber diaphragm 14 for distinction is connected on the side to the housing part 16. A respective valve 18, 20, which releases or closes the inflow opening or outflow opening synchronously with the pump cycle, is associated with the inflow opening or each inflow opening as well as with the outflow opening or each outflow opening.

The pump cycle is obtained during the operation of the pump 1 on the basis of a respective drive of the pump 1. A rotating drive (crank drive), whose rotary motion is converted by means of a disk with an eccentrically arranged crank pin (eccentric disk 22) or the like into an oscillating, linear motion of a driving rod (connecting rod) 24 acting on the chamber diaphragm 14 in a manner known basically per se, is used as a drive in FIG. 1. FIG. 2 shows an electromagnetic drive (coil 26 with a driving rod 24 that is ferromagnetic in at least some sections), which acts directly on the driving rod 24 and likewise leads to an oscillating, linear motion of the driving rod 24 acting on the chamber diaphragm 14 together with a spring element 28 exerting a resetting force. A pump 1 of this type is called oscillating armature pump and the part of the driving rod 24 that is ferromagnetic in at least some sections is correspondingly called armature 30. The driving rod 24 is guided in a guide 32.

Based on the axially oscillating motion of the driving rod 24, the chamber diaphragm 14 is tensioned or released cyclically. The chamber diaphragm 14 is tensioned during the return stroke of the driving rod 24 and this results in an increase in the volume of the chamber 12. The chamber diaphragm 14 is released during the forward stroke of the driving rod 24, and this results in a reduction in the volume of the chamber 12. This correspondingly applies to a piston 34 (FIG. 9) driven by means of the driving rod 24. When the chamber volume is enlarged, a respective medium flows into the chamber 12 via the inflow opening or each inflow opening. At least part of the medium having flowed previously into the chamber 12 is displaced from the chamber 12 through the outflow opening or each outflow opening during the subsequent reduction of the chamber volume. The result is, in a manner known per se, a volume flow of the medium being delivered and/or a pressure reduction upstream of the pump 1 and/or a pressure increase downstream of the pump 1.

The view in FIG. 3 shows in a schematically simplified manner an electroactive diaphragm 40 (electroactive film 40). This may be an electroactive diaphragm 40 hereinafter also called diaphragm 40 for short in the form of an electroactive polymer (EAP) or of a dielectric elastomer (DEA). Both variants will always be implied below whenever the diaphragm 40 or a diaphragm 40 is mentioned.

Electroactive polymers and dielectric elastomers are basically known per se. A diaphragm 40—or generally an electroactive diaphragm 40 -, which is formed from it is known to change its aspect ratio (ratio of thickness to area) as a function of an applied electric potential. In addition or as an alternative, the elasticity of such a diaphragm 40 can also be set, so that a rigid and inflexible or only slightly flexible diaphragm or an elastic, flexible diaphragm will be obtained depending on the applied potential, as this is described, for example, in US 2004/124384 A1 (US 2004/124384 A1 is incorporated by reference herein in its entirety).

A diaphragm 40, to which no electric potential is applied, is shown in the upper area of the view in FIG. 3. The same diaphragm 40 is shown directly under it in case of application of an electric potential. As can be seen, the thickness of the diaphragm 40 is reduced because of the application of an electric potential. The area of the diaphragm 40 has increased in the process. This can only be seen in the view in the form of an increase in the extension of the diaphragm 40 along one of the axes thereof, i.e., in the form of a change in length.

The application of an electric potential to a diaphragm 40 is shown in the view in FIG. 3 in the form of two lines 42, 44 acting on the diaphragm 40. The lines 42, 44 lead to an electric power source, not shown, so that an electric potential can be applied to the respective diaphragm 40 by means of the lines 42, 44. These lines 42, 44 are not shown in the case of a diaphragm 40 to which no electric potential is applied. These lines 42, 44 are, of course, actually present in a concrete embodiment of the invention described below regardless of whether or not an electric potential is applied to the diaphragm 40 in question. The application of an electric potential to a diaphragm 40 is controlled, for example, by means of a circuit component present in a circuit with the lines 42, 44, for example, by means of an electronic switch in the form of a transistor or the like, in a manner that is basically known per se. The Figures show features which are to be the interpreted that the circuit component has applied electric potential when the electric lines 42, 44 are visible, representing a diaphragm 40 to which an electric potential is applied, whereas no electric potential is applied to a diaphragm 40 in the figures that do not show such visible lines 42, 44 in the particular view shown.

The lower part of the view in FIG. 3 shows two diaphragms 40, which together form a diaphragm pair. In the released, i.e., potential-free state, these are arranged in the same plane next to each other and adjoining each other. A spring element is placed in the area in which the two diaphragms 40 adjoin each other. In case of a potential applied to the diaphragm 40, the modulus of elasticity of the two diaphragms 40 changes as well, and the diaphragms 40, which have become flexible because of the applied electric potential, are partly lifted by the spring element, as this is shown in the view being shown.

A special feature should be pointed out in the interpretation of the following figures based on the view in the lower part of FIG. 3. The following applies in case of diaphragms 40 belonging together in pairs, i.e., a diaphragm pair as in the view in the lower part of FIG. 3, or in case of a plurality of diaphragms 40 belonging together: Even if lines 42, 44 connected to a diaphragm are shown for one diaphragm 40 only in the interest of clarity of the view (and application of one electric potential is thus shown), this, i.e., the application of the electric potential, also applies to the other diaphragm 40 of the diaphragm or pair or to every other diaphragm 40 belonging to the diaphragms belonging together. Consequently, an electric potential is either applied always simultaneously or an electric potential is not applied to diaphragms 40 belonging together.

Based on the explanations given above on the basis of FIG. 3, the view in FIG. 4 shows a first embodiment of a pump 10 of the type according to the invention, wherein reference is made to the description of FIG. 1 regarding known components of the pump 1 which are also present in the pump 10 according to the invention.

The view in FIG. 4 shows on the left-hand side the driving rod 24 at the lower summit and on the right-hand side at the upper summit of the oscillating motion. A situation with a maximum volume of the chamber 12 is correspondingly shown on the left-hand side. When the chamber volume increases, the medium in question flows into the chamber 12 up to the shown position of the chamber diaphragm 14. By contrast, a situation with minimum volume of the chamber 12 is shown on the right-hand side. The medium in question is displaced from the chamber 12 during a reduction of the chamber volume up to the shown position of the chamber diaphragm 14.

The motion of the chamber diaphragm 14—or alternatively the motion of a piston 34 (FIG. 9)—arises from the oscillating motion of the driving rod 24 guided in a guide 32. However, the motion of the driving rod 24 does not arise now (contrary to the views in FIG. 1 and FIG. 2) any longer from a crank drive or a linear drive of the type shown in FIG. 1. Rather, the drive of the driving rod 24 takes place by means of at least one electroactive diaphragm 40 or of a plurality of electroactive diaphragms 40 distributed symmetrically around the driving rod 24 in the radial direction as well as by means of a resetting element acting in the opposite direction.

The diaphragm or each diaphragm 40 acts, on the one hand, on the outer surface of the driving rod 24 and, on the other hand, on a housing of the pump 10. In case of an electric potential applied to the diaphragm 40 or each diaphragm (FIG. 4: View on the left-hand side), the effective length of the diaphragm 40 or each diaphragm between the location at which it is arranged, for example, on the pump housing, on the one hand, and at the driving rod 24, on the other hand, increases. A resetting element 28 acting on the driving rod 24, for example, a spring element 28, especially a spring element 28 in the form of a coil spring acting as a tension spring, then deflects the driving rod 24 corresponding to the increased effective length of the diaphragm or each diaphragm 40, so that a return stroke of the driving rod 24 and correspondingly a return stroke of the chamber diaphragm 14 will occur. This leads to the above-described increase in the chamber volume. As soon as an electric potential is not applied any longer to the diaphragm 40 or each diaphragm (FIG. 4: View on the right-hand side), the original—shorter—effective length of the diaphragm or each diaphragm 40 will be restored. The driving rod 24 is moved by means of the diaphragm or each diaphragm 40 in the direction of a forward stroke against the force of the resetting element 28. A forward stroke of the chamber diaphragm 14—or of a piston 34—will thus take place as well, and this leads to the reduction of the chamber volume, which was already described above.

In summary, the motion process of the embodiment of the pump 10 as shown in FIG. 4 can thus be described as follows: During the forward stroke, the diaphragm 40 or each diaphragm pulls the driving rod 24 against the resetting force of the resetting element 28. During the return stroke, the length and the elasticity of the diaphragm 40 is increased because of the electric potential applied to the diaphragm 40 or each diaphragm 40, so that the action of the restoring force of the resetting element 28 prevails and the resetting element 28 correspondingly deflects the driving rod 24 in the direction in which the resetting force acts.

The cyclical application of an electric potential to the diaphragm 40 or each diaphragm leads to a corresponding cyclical motion of the driving rod 24 as well as to a cyclical motion of the chamber diaphragm 14 or of a piston 34, which is associated therewith. This leads to the pumping effect known per se. The resulting stroke of the pump 10 is the distance between the two parallel auxiliary lines designated by H.

In case of an individual diaphragm 40 in a pump housing, which is, for example, cylindrical, the diaphragm 40 acts, on the one hand, on the outer surface of the driving rod 24 and, on the other hand, for example, on the inner jacket surface of the pump housing. The connection of the diaphragm 40 to the pump housing may be established, for example, by the diaphragm 40 being fixed by clamping on sides of the pump housing between two components of the pump housing along the circumferential line of the pump housing or in some sections along this circumferential line. For example, bonding to the inner jacket surface of the pump housing may be considered as an alternative. Very similarly, the connection of the diaphragm 40 to the driving rod 24 may be established, for example, by the diaphragm 40 being clamped between two parts of the driving rod 24 or by the diaphragm 40 being bonded to the driving rod 24.

As an alternative to the embodiment shown in FIG. 4, an embodiment based on the same principle with the action of the force transposed is conceivable. The diaphragm or each diaphragm to which no electric potential is applied now acts in the direction of a return stroke and the resetting force (opposing force) bringing about a forward stroke when an electric potential is applied is generated, for example, by means of a disk spring or coil spring acting as a compression spring.

The view in FIG. 5 shows an embodiment of a pump 10, which is based on the embodiment shown in FIG. 4, so that reference is made to the details explained on the basis of FIG. 4 to avoid repetitions. In the embodiment according to FIG. 5, at least one additional electroactive diaphragm 40′ assumes the function of the resetting element. For distinction, the diaphragm 40 or each diaphragm, which applies the force for the forward stroke, is called forward stroke diaphragm 40, and the diaphragm 40′ or each diaphragm, which applies the force for the return stroke, is called return stroke diaphragm 40′. The forward stroke diaphragm 40 is the diaphragm that is located, on the whole, closer to the chamber diaphragm 14 than the return stroke diaphragm 40′ in the embodiment shown in FIG. 5. This order along the longitudinal extension of the driving rod 24 is not obligatory. It is essential that in a state in which no electric potential is applied, a force be able to be exerted by means of at least one diaphragm 40 to the driving rod 24, which force leads to a forward stroke (actuating stroke) of the pump 10 (actuating/forward stroke diaphragm 40) and that in a state in which no electric potential is applied, a force be able to be exerted to the driving rod 24, which force leads to a return stroke of the pump 10 (return stroke diaphragm 40).

An electric potential is alternatingly applied to the forward stroke diaphragm 40 or each forward stroke diaphragm as well as the return stroke diaphragm 40′ or each return stroke diaphragm for an oscillating motion of the driving rod 24 and hence for an oscillating motion of the chamber diaphragm 14—or of a piston 34—for the pump drive, so that the effective length of the forward stroke diaphragm 40 is either alternatingly increased (FIG. 5, left) and the action of the force of the return stroke diaphragm 40′ prevails and a return stroke will result, or else the effective length of the return stroke diaphragm 40′ is increased (FIG. 5, right), and the action of the force of the forward stroke diaphragm 40 accordingly prevails and a forward stroke of the pump 10 will correspondingly occur.

The invention being proposed here has hitherto been explained on the basis of an especially simple actuation of the electroactive diaphragm 40, 40′ or each electroactive diaphragm. The respective electric potential is either applied or not applied here to the respective diaphragm 40 or a diaphragm 40, 40′. It is, of course, also possible to apply the electric potential available based on the respective electric power source more or less only partly to an electroactive diaphragm 40, 40′.

For the embodiment shown in FIG. 4, this means that the extent to which the driving rod 24 can be retracted by means of the resetting element 28 can be set by means of the particular electric potential applied to the diaphragm 40 or each diaphragm shown there. The maximum deflection of the driving rod 24 during a return stroke determines the maximum volume of the pump chamber 12. A high electric potential results in a greater increase in the length of the diaphragm 40 or each diaphragm, so that the driving rod 24 can be retracted to a correspondingly great extent. A lower electric potential results in a smaller increase in the length of the diaphragm 40 or each diaphragm, so that the driving rod 24 can be retracted to a correspondingly lower extent. A higher electric potential correspondingly results in a greater maximum chamber volume. This can thus be set by means of the respective applied electric potential (within the framework of the elasticity of the chamber diaphragm 14 or within the framework of the range of motion of the piston 34). The resulting oscillation amplitude of the driving rod 24 determines the change in the volume of the pump chamber 12 and hence, for example, the volume (flow) of the medium being delivered per unit of time (during a pump cycle; during a return stroke and a subsequent forward stroke) by means of the pump 10.

The duration of a unit of time, i.e., the duration of a pump cycle, can advantageously be set here precisely as well. Reference is made for this to the views in FIG. 6 and FIG. 7. Accordingly, to set a duration of a pump cycle, a potential according to a predefined or predefinable first voltage profile 50 (return stroke voltage profile 50) is applied to the diaphragm 40 or each diaphragm during the return stroke, and a potential according to a predefined or predefinable second voltage profile 52 (forward stroke voltage profile 52) is applied to the diaphragm 40 or each diaphragm during the forward stroke. The forward and return stroke voltage profiles 50, 52 may be symmetrical, as this is shown in the views in FIG. 6 and FIG. 7. However, this is not necessary, and the forward and return stroke voltage profiles 50, 52 may also be different. The sum of a particular duration (t_(R), t_(V)) of the return stroke voltage profile 50 and of the forward stroke voltage profile 52 determines the overall duration of a pump cycle of the pump 10 and can be set, for example, by changing the slope of the forward stroke and return stroke voltage profiles 50, 52.

Even though linear and monotonically rising and falling return stroke and forward stroke profiles 50, 52 are shown in the view in FIG. 7 in the interest of simple conditions, each profile 50, 52 may be composed, for example, from a plurality of sections that are straight in sections with respective different slopes. As an alternative or in addition, it is also possible for at least individual sections of a profile 50, 52 or both profiles 50, 52 to follow a mathematical function, for example, a trigonometric function or an exponential function.

The view in FIG. 7 shows a return stroke voltage profile and a forward stroke voltage profile 50, 52, respectively, which corresponds essentially to the switching on and to the switching off of the potential applied to the diaphragm 40 or each diaphragm. The change over time in the volume of the pump chamber 12 is also determined by the respective resetting force. Such profiles 50, 52 can be embodied in an especially simple manner.

It is generally true that in the embodiment shown in FIG. 4, an electric potential (V_(Rtn)) between a lower threshold value (V_(min)>0 V) and an upper threshold value (V_(max)), for example, the maximum available potential based on the electric power source, is applied to the diaphragm 40 or each diaphragm for a return stroke, and an electric potential (V_(Act)) between the upper threshold value (V_(max)) and the lower threshold value (V_(min)) is applied to the diaphragm 40 or each diaphragm for a forward (actuating) stroke: V_(Rm)=[V_(min) . . . V_(max)]; V_(Act)=[V_(max) . . . V_(min)]. By selecting the lower and upper threshold values (V_(min) and V_(max)), the two outer summits of the oscillating motion of the driving rod 24 and hence the pump stroke can be set precisely. This means that the change in the volume of the pump chamber 12 can be set precisely during a pump cycle (return stroke and subsequent forward stroke). By selecting the duration (t_(R)) of the return stroke and by selecting the duration (t_(V)) of the forward stroke, the stroke frequency of the pump 10 can be set precisely. By predefining the return stroke voltage profile 50 and by predefining the forward stroke voltage profile 52, the change over time in the volume of the pump chamber 12 during the pump cycle can be set precisely, optionally even independently from one another for the two partial strokes. All these possibilities of setting may be combined with one another, but may also be used individually. The latter happens, for example, if “only” the stroke volume of the pump 10 is set by predefining the lower threshold value and the upper threshold value (V_(min), V_(max)).

The explanations based on FIG. 6 and FIG. 7 correspondingly also apply to the embodiment of a pump 10, which is shown in FIG. 5. Just as this was explained above, the respective effective force of the return stroke diaphragm 40′ can also be set additionally for said return stroke diaphragm acting as a resetting element by predefining the respective applied potential.

The view in FIG. 8 shows as examples of this possible volumes of the pump chamber 12 resulting from such a possibility of setting at the end of a return stroke (FIG. 8; left) and at the end of a forward stroke (FIG. 8; right). Electroactive diaphragms 40 are not shown here in the interest of clarity. At least one diaphragm 40 according to FIG. 4 or at least one forward stroke diaphragm 40 as well as at least one return stroke diaphragm 40′ according to FIG. 5 may correspondingly be added conceptually. In the views in the upper part of FIG. 8, the corresponding V_(max) is markedly greater than in the views in the lower part of FIG. 8. In the views in the lower part of FIG. 8, the corresponding V_(max) approximately corresponds to the V_(min) in the views in the upper part of FIG. 8.

The views in FIG. 8 show a pump 10 with a piston 34 instead of the chamber diaphragm 14 shown hitherto. It was already mentioned farther above that a piston 34 may also always be considered for use as an alternative as a means for periodically changing the volume of the pump chamber 12 even in the embodiments that show a chamber diaphragm 14 as a means for periodically changing the volume of the pump chamber 12 instead of the chamber diaphragm 14 used there. It was shown in FIG. 8 that by predefining the electric potential, which is applied to the diaphragm 40 or each diaphragm or to the forward stroke diaphragm 40, 40′ or each forward stroke diaphragm, a middle position can be set, around which the driving rod 24 and hence also the chamber diaphragm 14 (or a piston 34) oscillates. By contrast, it is shown in FIG. 9 by means of lower (return stroke) and upper (forward stroke) piston positions, which are drawn by broken lines, that the stroke volume can also be set by predefining the electric potential, which is applied to the diaphragm 40 or each diaphragm or to the forward stroke diaphragm and the return stroke diaphragm 40, 40′ or to each diaphragm. The two possibilities of setting shown on the basis of FIG. 8 and FIG. 9 may, moreover, also be combined.

The view in FIG. 10 finally shows a special embodiment of a pump 10 on the basis of pump 10 shown in FIG. 5. The special feature is that the at least one electroactive diaphragm acting as a forward stroke diaphragm 40 and the at least one electroactive diaphragm acting as a return stroke diaphragm 40′ act cyclically either as an actuator or as a sensor. The function as an actuator has been described so far and the oscillating motion of the driving rod 24 arises from the function as an actuator. The function as a sensor is based on the fact that an indicator can be determined for the respective aspect ratio (ratio of thickness to area) of the diaphragm 40, 40′ by means of a capacitance measurement. The particular capacitance determined as an indicator of the respective effective length of the diaphragm 40, 40′ and hence also an indicator of the axial position of the driving rod 24. The axial position of the driving rod 24 is, in turn, an indicator of the position of the pump 10, so that position measured values, which can be used for regulating the pump 10, can be obtained by means of a capacitance measurement. A special embodiment of a pump 10 of the type proposed so far is correspondingly based on the fact that the position of the driving rod 24 is regulated (position regulation) and/or the speed of motion of the driving rod 24 (speed regulation) is regulated by means of a position measured value that can be obtained based on capacitance measurement on at least one diaphragm 40, 40′. The alternating function of the diaphragms 40, 40′ as an actuator or sensor is shown in the view shown in FIG. 10 by showing additional lines (measuring lines) 46, 48 for capacitance measurement in addition to the lines 42, 44 for applying an electric potential to the respective diaphragm 40, 40′.

A diaphragm 40, 40′ acting at least at times as a sensor in this sense makes it possible to detect the motion process of the pump 10 and makes possible, for example, modes of operation of the pump 10 with constant pump frequency, constant stroke, constant force, and constant change in the volume of the pump chamber 12 over time by means of a corresponding regulation. In addition, functional combinations of the above-mentioned modes of regulation are also possible.

Individual aspects of the description submitted here, which are in the foreground, can thus be summed up briefly as follows: Proposed are a chamber pump 10 and a method for operating same. The chamber pump 10 comprises, in the manner known per se, a pump chamber 12, a chamber diaphragm 14 or a piston 34 as means for displacing the volume of the pump chamber 12, as well as a driving rod 24, which is axially movable and acts on the chamber diaphragm 14 or on the piston 34 to change the volume of the pump chamber 12. The chamber pump 10 being proposed here is characterized in that it comprises at least one electroactive diaphragm 40, 40′, which acts as an actuator for influencing an axial position of the driving rod 24 and acts on the driving rod 24, on the one hand, as well as on a housing of the pump 10, on the other hand, and that an electric potential is applied to the at least one electroactive diaphragm 40, 40′ during the operation of the chamber pump 10 to influence an axial position of the driving rod 24 and to achieve a return stroke or a forward stroke of the chamber pump 10.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

APPENDIX: LIST OF REFERENCE DESIGNATIONS

-   1 Pump/chamber pump -   10 Pump/chamber pump -   12 Pump chamber -   14 Chamber diaphragm -   16 Housing part -   20 Valve -   22 Eccentric disk -   24 Driving rod -   26 Coil -   28 Spring element, resetting element -   30 Armature -   32 Guide -   34 Piston -   36, 38 (Blank) -   40, 40′ Electroactive diaphragm -   42, 44 Line (for applying an electric potential to an electroactive     diaphragm) -   46,48 Line (for capacitance measurement on an electroactive     diaphragm) -   50 Return stroke voltage profile -   52 Forward stroke voltage profile 

What is claimed is:
 1. A chamber pump for use in a medical device or in a safety system, the chamber pump comprising: a chamber pump housing; a chamber diaphragm or a piston, the chamber diaphragm or the piston cooperating with the chamber pump housing to form a pump chamber with the chamber diaphragm or the piston changing the volume of the pump chamber; an axially movable driving rod acting on the chamber diaphragm or on the piston for changing the volume of the pump chamber; an electroactive diaphragm acting on the driving rod as an actuator for influencing an axial position of the driving rod to deflect the driving rod in a first direction, wherein the electroactive diaphragm acts with a driving force that is applied on the driving rod and on the chamber pump housing; and a resetting element applying a resetting force deflecting the driving rod in a second direction opposite to the first direction, wherein the resetting element comprises an additional electroactive diaphragm acting as an actuator on the driving rod and on a housing of the pump.
 2. A chamber pump in accordance with claim 1, wherein the driving force exerted on the driving rod by the electroactive diaphragm is directed antiparallel to the resetting force exerted on the driving rod by the additional electroactive diaphragm.
 3. A chamber pump in accordance with claim 2, wherein: the electroactive diaphragm acts on the driving rod at a location closer to the chamber diaphragm or the piston as compared to the additional electroactive diaphragm; the electroactive diaphragm acts on the chamber housing at a location closer to the chamber diaphragm or the piston than to a location the electroactive diaphragm acts on the driving rod; and the additional electroactive diaphragm acts on the driving rod at a location that is closer to the chamber diaphragm or the piston than a location at which the additional electroactive diaphragm acts on the chamber housing.
 4. A chamber pump in accordance with claim 1, wherein the electroactive diaphragm forms a sensor for obtaining position information regarding a position of the chamber diaphragm or of the piston.
 5. A chamber pump in accordance with claim 4, wherein the electroactive diaphragm and the additional electroactive diaphragm act alternatingly as actuator and as sensor.
 6. A method for operating a chamber pump, the method comprising the steps of: providing the chamber pump, wherein the chamber pump comprises a chamber pump housing, a chamber diaphragm or a piston, the chamber diaphragm or the piston cooperating with the chamber pump housing to form a pump chamber with the chamber diaphragm or the piston changing the volume of the pump chamber, an axially movable driving rod acting on the chamber diaphragm or on the piston for changing the volume of the pump chamber, an electroactive diaphragm acting on the driving rod as an actuator for influencing an axial position of the driving rod to deflect the driving rod in a first direction, wherein the electroactive diaphragm acts with a driving force that is applied on the driving rod and on the chamber pump housing; and a resetting element applying a resetting force deflecting the driving rod in a second direction opposite to the first direction, wherein the resetting element comprises an additional electroactive diaphragm acting as an actuator on the driving rod and on a housing of the pump; and applying an electric potential to the electroactive diaphragm or to the additional electroactive diaphragm for influencing an axial position of the driving rod and for achieving a return stroke or a forward stroke of the chamber pump.
 7. A method in accordance with claim 6, further comprising applying an electric potential to the electroactive diaphragm or to the additional electroactive diaphragm for influencing an axial position of the driving rod and for achieving the other of the return stroke or the forward stroke of the chamber pump; and alternating between or in a phase-shifted manner changing between the return stroke and the forward stroke for achieving an oscillating motion of the driving rod.
 8. A method in accordance with claim 7, wherein the electric potential is applied to the electroactive diaphragm corresponding to a predefined or predefinable first voltage profile; and the electric potential is applied to the additional electroactive diaphragm corresponding to a predefined or predefinable second voltage profile.
 9. A method in accordance with claim 7, wherein position information concerning a position of the chamber diaphragm or of the piston is determined by means of the electroactive diaphragm in a form of a capacitance measurement.
 10. A method in accordance with claim 7, wherein: an electric potential is alternatingly applied to the electroactive diaphragm or a capacitance of said electroactive diaphragm is measured to obtain position information; or an electric potential is alternatingly applied to the additional electroactive diaphragm or a capacitance of said additional electroactive diaphragm is measured to obtain position information.
 11. A method in accordance with claim 9, wherein the position information acts as an actual value for regulating the volume of the chamber pump. 